Circuit controller



, I Sept. l I H LAMBERT '1 CIRCUIT CONTROLLER v- F'iled June 26, 1943INVENTOR ATTORNEY 5 placed; with which Patented Sept. 26, 1944 CIRCUITCONTROLLER Harry L. Lambert, Wales Addingr N.

Eniield, N. Y., assignor to Allen Machine Corporation, Ithaca,

Application June 26, 1943. Serial No. 492,394

(Cl. 20G-80) 16 Claims.

This invention relates to electric circuit controllers, and moreparticularly to mercury tube switches which may be employed i'orcontrolling an electric circuit in response to varying centrifugalforces.

One object of the invention is to improve circuit controllers wlthmercury tube switches of the type which are operated by centrifugalforces.

Another object of the invention is to provide an improved mercury tubeswitch which may be operated by centrifugal forces to open or close acircuit at a selected speed; which may be rotated in order to create thecentrifugal forces that open and close the circuit; which may be mounteddirectly on a shaft of an electric motor for rotation therewith; whichmay be employed to control the speed of such motor and maintain itwithin relatively close limits; with which the maximum speed above whichit will not allow the motor to run may be varied or adjusted selectivelywithin a considerable range; which will operate to control a circuit ata selected speed in any position in which the switch and motor may beplaced; with which the speed at which the switch will operate to alterthe condition of a circuit therethrough will be substantiallyindependent of the position in which it is the mercury tube of theswitch may ybe easily replaced in a simple manner; and which will berelatively simple, compact and inexpensive.

Other objects and advantages'will be apparent from the followingdescription o1' one embodiment of the invention, and the novel featureswill be particularly pointed out hereinafter in connection with theappended claims.

In the accompanying drawing:

Fig. 1 is a side elevation of a motor having a mercury tube switchmounted on the shaft thereof and formed in accordance with thisinvention, the switch and part of its mounting being shown in section;

Fig. 2 is a transverse sectional elevation of the same, the sectionbeing taken approximately along the line 2-2 of Fig. 1; and

Fig. 3 is a sectional elevation through a portion of the mercury tubeswitch and representing the position taken by the mercury body inresponse to centrifugal forces when opening the circuit.

In the illustrated embodiment of the invention, the mercury tube switchis shown as mounted upon the shaft I of the armature of any desiredelectric motor 2 of any suitable type, whose speed is to be controlled.The windings of this motor are shown only conventionally anddiagrammatically at. 3. Mounted removably upon the outer end of theshaft I is a body or mass 4 of suitable insulating material. This bodyor mass 4 may be provided with a metallic sleeve or bushing 5 extendingin a direction from face to face thereof at a central zone, and whichremovably and telescopically nts the shaft I. This bushing 5 is providedat one end with a collar l which spaces the mass 4 from the face 'I of aboss 8 cn the end oi the motor 2. The collar l may have a set screw 9engageable with the shaft I by which the bushings 5 may be removablysecured on the end of the shaft I, but coupled thereto for rotationtherewith. The periphery of the bushing l may have a knurled orroughened surface, and when the mass 4 is molded thereon, this providesa driving connection between them.

The mass 4 is provided on its outer end face with an elongated recess III, disposed with its longitudinal axis generally radially of the axisof shaft I, and a rod or screw II extends across the recess I0 andthrough the portions of the block at the ends of the recess. The portionof the screw I I within the recess is threaded, and the end portionsWithin the mass 4 are provided With smooth peripheral surfaces which arerotatably mounted in the mass 4. The head I2 o1 the screw II iscountersunk into the mass 4 at the periphery of the latter, so as tolimit movement of the screw endwise in one direction, and the other endof the screw II is provided with an annular groove I 3 in the portionprojecting into a shallow cavity I4 in the periphery oi mass 4. .Abifurcated clip or washer I5 is passed into straddling relation with thescrew II in a groove I3 thereof so as to limit endwise movement oi' thescrew II in the opposite direction.

A nut or block I6 is disposed in the recess I0 for endwise slidingmovement therealong, and this block has aI threaded passage therethroughfrom face to face through which the threaded portion of the screw II isthreaded. The nut I Ii is held against rotation on the screw II by theside walls of recess Il), and rotation oi' screw II will cause the nutI6 to move endwise along I the recess III in one direction or the other,depending upon the direction oi rotation of screw II. The head I2 of thescrew and the washer I5 prevent endwise movement of the screw withoutlimiting its rotary movement.

Secured to the outer face of the nut IB is a simple, biiurcated springclamp Il which receives and removably clamps between its arms a mer- Theclamp Il is also procury tube switch I 8.

vided with an angular arm I9 which extends around one end of the mercurytube switch I8, so as to limit its endwise movement in the clamp |1. Acushion 2Il, such as of felt or sponge rubber, is interposed between thearcuate end of the arm I9 and the abutting end of the switch I8. Theswitch I8 includes a tube or housing 2| with an elongated chamber 22therein. Conductors 23 and 24 extend through the tube or housing 2| intoone end of said chamber 22 in spaced relation to each other and extendpartially across the chamber 22, and there terminate in exposedconducting portions which may be engaged by a globule or small mass 25of a conducting liquid, such as mercury in liquid form. The outer endsof the conductors 23, 24 are connected by flexible leads 26 and 21respectively to terminal screws 28 and 29 respectively, which in turnextend through the mass 4 and are connected to collecting rings 3D and3| mounted on the end face of the mass 4 facing the motor. The rings 30and 3| are concentric with the shaft.

Suitable brushes 32 and 33 are suitably mounted on the boss 8 on the endof the motor, so as to bear against the rings 3U and 3| and provideelectrical connections therewith as the mass or body 4 rotates with thearmature shaft. The brush 32 is connected with one end of the winding 3of the motor, and the brush 33 is connected to a lead 34 which serves asa lead to the motor. The other end of the winding 3 is connected to alead 35 extending exteriorly of the motor 2. Leads 34 and 35, whenconnected to a source of electrical current, will provide an operatingcurrent to the motor 2.

The mercury tube switch I8 is mounted eccentrically to the axis ofrotation of the shaft I, with the longitudinal axis of chamber 22crosswise of the axis of shaft I, so that the end of the chamber 22containing the mercury will be at one side of the axis of the shaft I.When said shaft is rotated, the mercury 25 will be thrown into andconfined in one end of the chamber 22, as shown in Fig. 1. The liquidmercury does not Wet the glass of which the tube is preferably formed,and the cross sectional area of the chamber 22 at the end having themercury 25 therein is small enough so that the mercury will be heldagainst lateral spreading and will have a pronounced convex meniscus onits exposed surface towards the conductors 23 and 24, These conductorsextend towards the mercury to such an extent that when the device isinactive and in the position shown in Fig. 1, with the mercury in theouter end of the chamber 22, the conductors 23 and 24 will extend intothe meniscus, so that the mercury will complete a circuit between theconductors 23 and 2 4.

At least one of these conductors will extend only partly across themeniscus. When the motor is operated, the centrifugal forces acting onthe body of mercury will tend to iiatten the meniscus which is engagedwith the conductors 23, 24. As the speed increases, this attening of themeniscus will carry t he mercury out of contact with at least one of theelectrodes 23 and 24, as shown in Fig. 3. This opens the circuit betweenthe electrodes 23 and 24, and thus opens the circuit through thewindings of the motor 2, with the result that the speedA of the motorwill fall. As soon as the speed of the motor decreases the centrifugalforces acting on the mercury 25 will decrease, and the mercury will, bythe action of its surface tension, tend to re-establish the normalmeniscus on its exposed surface, andas this reformation of the normalmeniscus continues, it will re-establish contact with the conductors 23and 24, and thus re-establish the circuit through the motor 2.

Since the mercury mass or body 25, when rotated, is confined against allmovement in the tube 2|, except for the iiattening of the meniscus underthe action of centrifugal forces, this switch is particularly suitablefor high speed motors. The leads 23 and 21 are exible and provided withsuicient slack so that the tube 2| may be shifted endwise to differentextents off center from the axis of the shaft by rotation of the screw IAs the mercury tube switch I8 is moved farther from the shaft I, thelower will be the speed of the motor at which the switch will operate toopen the circuit, for the reason that when the mercury body 25 isfarther from the axis of rotation, the centrifugal forces acting thereonfor a given speed will be greater. By shifting the mercury tube switchtoward the axis of rotation of the shaft l, a higher speed of rotationwill be required to create the centrifugal force necessary to open thecircuit of the motor. Thus, the desired speed of the motor may bepredetermined and selected merely by rotation of the screw Il in onedirection or the other, so as to shift the mercury tube switch IB towardand from the axis of rotation of the shaft I.

The brushes 32 and 33 provide a continuous connection between the leads26 and 21 from the mercury tube switch, and the power line and windingsof the motor 2. A cap 35 may be telescoped frictionally over the end ofthe mass 4, so

as to enclose and protect the mercury tube switch I8 and its mountingmechanism against danger from outside blows, and this cap 36 may have anaperture 31 therein alined with the head of the screw I2'so that one mayinsert a screwdriver in the usual slot in the head I2 of the screw andenable turning of the screw II to adjust the mercury tube switch i8 forthe desired speed.

The tube 2| is closed, and the chamber 22 thereof is exhausted of airand replaced with an inert gas, as usual with mercury tube switches, sothat there will be no deterioration of the switch in use. It will beunderstood that the housing 2i of the switch is preferably, and mayadvantageously be, made of glass or similar material not wet by mercury,because of the ease in exhausting the chamber 22 of the tube and thereplacement of it with an inert gas, but this housing 2| may be made ofa suitable metal or other material not wet by mercury, For example, pureiron may be employed for the material of the housing 2|, because suchiron is ductile and easily worked, and a housing made thereof may beclosed at its ends through which the conductors 23 and 24 extend by asuitable glass which has approximately the same coefficient of expansionas the material of the conductors 23 and 26|. Theseconductors 23 and 24are also usually made of iron or other material inert-to mercury and notwet by it. When the housing 2| is made of a conducting material, such aspure iron, it is not necessary to have two electrodes 23 and 24, becausein that case the housing itself may serve as one electrode or conductor,and the other conductor is insulated from the material of the housingand extended partially across the chamber 22 and slightly intothe-meniscus of the mercury body.

1t will be understool that while the mercury tube switch is shown inseries with the windings of the motor for controlling the motor, whichis a common arrangement for small high speed motors, such as theelectric motors of dry shavers, nevertheless, this mercury tube switchmay control a relay circuit, and the relay used to control the motorcircuit where the motor is a relatively large one and uses currentbeyond the carrying capacity of the mercury switch. By the use of arelay, the mercury tube switch may be made relatively small and yet maycontrol a relatively large motor.

The mercury tube switch formed in this manner may also be mounted on anyrotary element and may be used to control any desired circuit, so as toopen or close a circuit at a critical speed, and this circuit socontrolled, either alone or through a relay, may control a signalcircuit or any other suitable circuit instead of a motor circuit.

While mercury is the preferred liquid as the conducting medium, becauseof its relatively high surface tension, which gives a pronouncedmeniscus, any other conducting liquid with substantial surface tensionis to be considered the broad equivalent of mercury, but when otherliquids are used, the materials of the housing and of the electrodesshould be those which are not wet by the liquid alone.

It will be observed that when the liquid is conilned in one end of theclosed chamber, the exposed surface of the conducting liquid normallycontacts a conductor, but is resiliently displaceable in a directionendwise of said chamber or radially of the axis of shaft I, whensubjected to the centrifugal forces created by rotation of the tube,sufficiently to interrupt contact between the liquid and a conductor andopen the circuit controlled thereby. In this illustrated example of theinvention, the surface tension of the mercury in forming the meniscusprovides the resilience opposing displacement of the exposed face of theliquid in a direction to withdraw from contact with said conductor andopen the ci'rcuit controlled thereby. It will be noted that the circuitwill be made in any position in which the device is placed, and thespeed at which the circuit will be opened is not dependent upon gravityor the position of the axis of rotation.

It is believed ythat the operation of this switch will be clear from theforegoing description and need not be given separately again.

It will be understood that various changes in details, materials,proportions and arrangements of parts, which have been herein describedand illustrated in order to explain the nature of the invention, may bemade by those skilled in the art within the principle and scope of theinvention as expressed in the appended claims.

I claim as my invention:

l. A mercury switch comprising a housing with an elongated chamber Whosewall is unwet by mercury, a body of mercury within and only partiallyfilling said chamber, said chamber having such a transverse crosssection at one end thereof that will impart to the mercury body whentherein by the surface tension on that body in opposition t gravity, apronounced convex meniscus, a conductor extending into said chamber andhaving solely within said meniscus portion of said body an exposedconducting surface, and conducting means electrically connected withsaid body to complete part of a circuit in which said mercury body, saidconductor and said conducting means are in series with one another,

and which may be broken by a flattening of said meniscus until itwithdraws from contact with said exposed surface of said conductor.

2. A mercury switch comprising a housing with an elongated chamber whosewall is unwet by mercury, a body of mercury within and only partiallyfilling said chamber, said chamber having such a transverse crosssection at one end thereof that will impart to the mercury body whentherein by the surface tension on that body in opposition to gravity, apronounced convex meniscus, a conductor extending into said chamber andhaving solely within said meniscus portion of said body an exposedconducting surface, conducting means electrically connected with saidbody to complete part of a circuit in which said mercury body, saidconductor and said conducting means are in series with one another, andwhich may be broken by a flattening of said meniscus until it withdrawsfrom contact with said exposed surface of said conductor, and meansmounting said housing for rotation about an axis to which thelongitudinal axis of said chamber is generally radial and with said oneend of the housing farther from said axis than the other end, wherebycentrifugal forces acting on said body may flatten said meniscus andopen said circuit through said body.

3. A circuit controller comprising a closed housing with a closedchamber therein whose wall is unwet by mercury, a body of mercury withinand only partially filling said chamber, said chamber having at one endthereof a transverse cross section that will impart to the mercuryconfined therein, by the, surface tension of the mercury in oppositionto gravity, a pronounced convex meniscus, and a pair of conductorsextending into said chamber and having, solely within said meniscusportion of said body, exposed conducting spaced surfaces, whereby themeniscus portion of said mercury completes an electric circuit betweensaid conductors which may be broken by a flattening of said meniscus bycentrifugal forces acting against said surface l tension until itwithdraws from contact with at least one of said exposed surfaces ofsaid conductors.

4. A circuit controller comprising a closed housing with a closedchamber therein whose wall is unwet by mercury, a body of mercury withinand only partially filling said chamber, said chamber having at one endthereof a transverse cross section that will impart to the mercuryconfined therein, by the surface tension of the mercury in opposition togravity,'a pronounced convex meniscus, a pair of conductors extendinginto said chamberand having, solely within said meniscus portion of saidbody, exposed conducting spaced surfaces, whereby the meniscus portionof said mercury completes an electric circuit between said conductors,and means mounting said housing for rotation about an axis, with saidone end of said housing farthest from said axis, whereby centrifugalforces acting on said body may flatten said meniscus to open the circuitfrom said said mercury body.

5. A mercury switch comprising a housing with an elongated chamber whosewall is unwet by mercury, a body o1' mercury within and only partiallyfilling said chamber, said chamber having such a transverse crosssection at one end thereof that will impart to the mercury body whentherein by the surface tension on that body in opposition to gravity, apronounced convex conductors through meniscus, a conductor extendinginto said charnber and having solely within said meniscus portion ofsaid body an exposed conducting surface, conducting means electricallyconnected with said body to complete part of a circuit in which saidmercury body, said conductor and said conducting means are in serieswith one another, and which may be broken by a attening of said meniscusuntil it withdraws from contact with said exposed surface of saidconductor, and means mounting said housing for rotation about an axis towhich the longitudinal axis of said,

chamber is generally radial and with said one end of the housing fartherfrom said axis than the other end, whereby centrifugal forces acting onsaid body may flatten said meniscus and open said circuit through saidbody, said mounting means including a holder for said housing, a rotarybase, and means carried by the base and interacting with said holder forshifting the latter in a direction toward and from the axis of rotationto vary the centrifugal forces acting on the body of mercury for anygiven speed of rotation of said housing about said axis.

6. A mercury switch comprising a glass tube with an elongated, closedchamber, a body of mercury within and only partially liing said chamberat one end thereof, said one end of said chamber having a transversecross section which will impart to the mercury confined therein, by theaction of the surface tension of the mercury in opposition to gravity, apronounced convex meniscus on its exposed face, a pair of' conductorsextending into said chamber from the end thereof opposite said one endand terminating within said mercury and at least one of them solelywithin said meniscus portion of said mercury body when said mercury isin said one end, whereby the mercury will normally complete an electriccircuit between said conductors in all possible positions of the tube,whereby when the meniscus is flattened by centrifugal forces actingthereon, the circuit will be broken between the meniscus and one of saidconductors.

7. A mercury switch comprising a housing with an elongated chamber whosewall is unwet by mercury, a body of mercury within and only partiallylling said chamber, said chamber having such a transverse cross sectionat one end thereof that will impart to the mercury body when therein, bythe surface tension on that body in opposition to gravity, a pronouncedconvex meniscus, a conductor extending into said chamber and havingsolely within said meniscus portion of said body an exposed conductingsurface, conducting means electrically connected with said body tocomplete part of a circuit in which said mercury body, said conductorand said conducting means are in series with one another, and which maybe broken by a iiattening of said meniscus until it withdraws fromcontact with said exposed surface of said conductor, said exposedconducting surface being spaced from the bottom of said meniscus adistance sufilcient to cause the meniscus to break contact with saidexposed surface when said meniscus is flattened by centrifugal forcesacting thereon.

8. A circuit controller comprising a tube with a closed chamber whosewall is unwet by mercury, a body of liquid mercury within and onlypartially filling said chamber and when within one zone of said chamberhaving a pronounced convex meniscus on its exposed face due to thesurface tension of the mercury acting in opposition to gravity, aconductor in said chamber and having an exposed portion within saidmeniscus only of said mercury, when said mercury is in said zone, andspaced far enough from the base of the meniscus that when the meniscusis flattened by centrifugal forces against its surface tension, contactis broken between said exposed conductor portion and said mercury, andmeans for connecting said mercury and said conductor in series.

9. A circuit controller comprising a tube with a closed chamber Whosewall is unwet by mercury, a body of liquid mercury within andV onlypartially. filling said chamber and when within one zone of said chamberhaving a pronounced convex meniscus on its exposed face due to thesurface tension of the mercury acting in opposition to gravity, aconductor in said chamber and having an exposed portion within saidmeniscus only of said mercury, when said mercury is in said zone, andspaced far enough from the base of the meniscus that when the meniscusis attened by centrifugal forces against its surface tension, contact isbroken between said exposed conductor portion and said mercury, meansfor connecting said mercury and said conductor in series in part of anelectric circuit to be controlled, and means mounting said tube forrotation about an axis with said chamber zone constituting a pocketfacing said axis and at one side thereof, whereby when said tube isrotated about said axis, the centrifugal forces on said mercury willtend to flatten said meniscus on its exposed face while the mercuryremains relatively immovable in said chamber pocket.

l0. A circuit controller comprising a tubewith a closed chamber whosewall is unwet by mercury, a body of liquid mercury Within and onlypartially filling said chamber and When within one zone of said chamberhaving a pronounced convex meniscus on its exposed face due to thesurface tension of the mercury acting in opposition to gravity, aconductor in said chamber and having an exposed portion within saidmeniscus only of said mercury, when said mercury is in said zone, andspaced far enough Afrom the base of the meniscus that when the meniscusis attened by centrifugal forces against its surface tension, contact isbroken between said exposed conductor portion and said mercury, meansfor connecting said mercury and said conductor in series, a spring clampremovably mounting said tube, a rotatable support, means mounting saidclamp on said support for movement of it and said tube towards and fromthe axis of rotation of said support with said zone of said chamberforming a pocket facing at its open side towards said axis, and meansfor maintaining electrical connections to said conductor and mercury inall rotary positions of said support.

1l. A circuit controller comprising a tube with an elongated, closedchamber whose wall is unwet by mercury, a body of liquid mercury withinand only partially filling said chamber, and when in one end of saidchamber having a pronounced convex meniscus on its exposed face, due tothe action thereon of its surface tension inv opposition to gravity, aconductor extending from approximately the other end of said chamberalong said chamber and only slightly into said meniscus of the mercuryat the other end of the chamber, and means for connecting said mercuryand said conductor in series in al1 locations of said mercury in saidchamber. v

l2. A circuit controller comprising a tube with

